Configuring MIME Types in IIS 7

Multipurpose Internet Mail Extensions (MIME) types identify the types of content that can be served to a browser or a mail client from a Web server. When a browser requests content from a Web server, the browser also requests the MIME type of that content. IIS returns this MIME type as the Content_Type field in an HTTP header before returning the content, so that the browser knows how to process or display that content.

IIS uses a default list of global MIME types to determine which types of content to serve. If a client requests a MIME type that is not defined on the Web server, IIS returns a 404.3 error.

You should enable only those MIME types that are required for the types of content stored on your Web server. This best practice helps reduce the server's attack surface.

For information about the levels at which you can perform these procedures, and the modules, handlers, and permissions that are required to perform this procedure, see MIME Types Feature Requirements (IIS 7).